"w_tom" wrote in message
...

Telco provides a "Service's accessible grounding means" in a
box called NID. Their 10 AWG earth ground wire connects their
NID box mounted outside (so that it is accessible) to that
earth ground rod. Some installers want to make that 10 AWG
wire look neat. They will even 'split bolt' attach it to the
breaker box ground wire. However better trained installers
will run their ground wire directly to the top of that ground
rod - as should be the CATV wire ground. All grounds should
run indepenently until they all meet at central earth ground.
This last requirement is not required in code but creates a
more robust and effective earth ground.

As a reminder to others, smart move to have all utilities
located before pounding down the rod.


There is no such thing as a "central earth ground" unless only _one_
grounding electrode is used.....a very poor practice in itself (with the
possible exception of a metal well casing)....much better to have _multiple_
grounding electrodes bonded together. All grounding electrodes are bonded
together to form a _single_ grounding electode _system_. The ground rod
that is being installed is merely a _supplement_ to the main grounding
electrode.......in this case the metal water pipe. Not a good idea to try
to dump all that on a single ground rod.......a single ground rod will in
fact become a choke to lightning trying to get into the ground. That single
ground rod should be supplemented by at least another ground rod 6 feet away
(or use a delta ground), or a ground ring can be installed with a minimum
#2.....and catch the cable TV while you are at it.

The basic idea is too run an unbroken GEC from the main panel to the
underground water pipe (min. #4) and suppliment that with a ground rod (or
two). Then bond all systems together. The idea is that when all the
systems are bonded together, ALL will come up to the same voltage (can be ma
ny thousands of volts), thus _not_ allowing a destructive current flow in
equipment served from different systems....like a modem. Don't forget to
jumper around the water meter and bond the hot water.

Bottom line, electric system grounding is a very misunderstood subject and
needs to be done by people who know and care about how to install it.

You still have your inside metal gas line to deal with.......you should call
your gas co. to see if they allow an (inside) connection to the electric
grounding system as required by NEC.

I hope that after going through all that trouble that you are also going to
install a lightning arrestor at the electric meter or service panel. Then
use a decent point of use surge protector for the computer that has
provision for power _and_ phone....cable too if you ever use a cable modem.

Also, since you said that you have a subpanel in another thread, you should
check to see that the subpanel is fed from the main panel with a _4_ wire
feeder (2 hots, neutral, equipment ground).